On the X-axis or Y-axis Properties window, click the Labels tab.
In the Axis heading box, type a word or phrase that you want to display along the axis of the chart.
In the Size list, type or select the size of the font used for the axis heading.
In the Color list, select the color that you want to use for the font. To modify the color, click More. To change the font, click Selector.
In the Angle box, type a value between +90 degrees and -90 degrees representing the rotation that you want to apply to the axis heading. In the list select the unit of angular measurement.
To keep the characters in the heading parallel to the x-axis, select Keep characters horizontal.